Centrifugal compressor or blower



April 12, O HOFFMANN CENTRIFUGAL COMPRESSOR OR BLOWER Filed Dec. 4, 1928 g N 7 m 7 Inventorz' Brumo H'oFF-momn, bk:I @664 His Attorney Patented Apr. 12, l 1932 LUNITED STATES f PAT N OFFICE, I

nnono HOFFMANN, or SPANDAU-WEST, GERMANY, ASSIGNOR T GENERAL nnnc'rnrc COMPANY, A CORPORATION or NEW YORK V o CENTRIFUG AL COMPRESSOR OR BLOWER i Application filed December 4, 1928, SerialNo.

- i The present invention relates to centrifugal compressors or blowers and especially to centrifugal compressors and blowers wherein the impeller is overhung on one end of the shaft with the suction side facing away from the bearing Centrifugalcompressors or blowers having their rotors arranged overhungwith'the suction side of the impellerfacing toward the bearing'have the disadvantage that as aresult of the adjacent end of the shaft bearlng,

- the starting up is effected unfavorably. The disadvantage is overcome by'arranging the overhung rotor so that the suction side of the twe-enthe bearing and the-impeller, a thing which tends to lengthen the'overhung portion of the shaft. As a result, arrangements of this kind have been limited heretofore to compressors or blowers for relatively small 7 pressures, for example pressures of the order of 0.1 to 0.2 atmospheres for in the case of higher pressures the packing or stufiingbox becomes sojlong in order to pack efficiently against the higher pressure that the overhang of the rotor wheel reaches toogreat a value. Particularly is this true in the case of impellers operating at relatively high speeds on account of the high stresses which occur in the long overhanging part of the shaft;

The object of the present invention is to provide an improved construction and arrangementin a centrifugal compressor or blower of the type wherein the suction side faces away from the shaft whereby an effective packing for relatively high pressures (for example pressures of the order of .5 atmosphere or greater) is obtained, while at the same time the length of the overhanging pornovel and my invention, attention is directed to the followingspecification and the claims appended thereto.

In the drawing the figure is a sectional through the be and an adjacent surface 'ing 8.

323,703, and in Germany December 8, 1927.

view of a centrifugal compressor or blower embodying the invention.

Referring to the drawing, 1 indicates the casing of a centrifugal compressor or blower having asuction inlet 2 and a discharge passage 3. In the casing is an impeller 4 overhung on the end of a shaft 5. The casing and impeller structure illustrated are shown only byway of example and are to-be taken as typical of any suitable, construction. Y The impeller sucks in thegas to be pumped, for example air, through the suction inlet 2 and discharges it through the discharge passage 3.

Connected to the left hand wall of easing;

"1, which"is the high pressure side of the cas- 'means that the length of the overhung portion of the shaft becomes relatively short. To this end, I provide arelatively short packing 10 located between the impeller and the forward end, of casing 6, such packing being-directly adjacent the end of bearing 8, and between the packing and the bearing I provide an annular space llwhich is sealed from the remainder of the casing 6 by a'suit- 'able packing 12. Asthe packing 12 is ar ranged between non-rotating parts it can be made tight easily. With this arrangement,

it will be seen that leakage from the dis- 1 charge side of the impeller to atmosphere must be through packing Q10 and thence aring so that the bearing serves as a part of the packing. g Y In" the present instance thestationary por-' tion of the packing is supported by an annular wall 13 which forms aj partjof' the compressor' casing, the packing 12'; being: ar-

ranged between the outer' end of wall 13 of-the shaft bear- The lowerportion of'bearing housing 6 .lfo'rms an oil chamber 14 to which oil. from the bearing flows by way of passages 15 which connect with a central bearing chamber 16. Oil is supplied to the bearing from any suitable source of oil pressure and flows from the bearing to chamber 14. The oil level in chamber 14 is maintained substantially constant by regulating the rate of withdrawal of oil therefrom, or in any other suitable way. Connected to chamber 11 is a pipe '17 which projects down into the oil in chamber 14 and serves to carry leakage oil from the right hand end of the bearing to oil chamber 14. The packing 10 is made of a length such, that pressure of the gas leaking from it to space 11 is substantially the same as the pressure of the oil leaking from the bearing to space 11 whereby the one pressure substantially balances the other. The height of the oil in chamber 14 is maintained at a value such that the pressure in space 11 will not be suflicient under normal operating conditions to force gas through pipe 17. In other words, the oil in chamber 14 serves as seal for pipe 17. Any leakage of gas from space 11 must be by way of the bearing to chamber 16, whence it may 'escape to atmosphere .or other region through passage 18 and pipe 19. The pressure of the oil flowing from the end of the bearing to space 11 depends upon the bearing pressure and the rate of rotation of the shaft. If, due

to abnormal operating conditions, the gas pressure in space 11 exceeds a predetermined high value the gas will blow out through pipe 17, thus safeguarding the oil film in the bear-ing. Thus it will be seen that the pipe 17 serves normally as a seal to prevent gas escaping around the packing and serves also as a safety device to permit discharge from space 11 in case the gas pressure therein becomes abnormally high.

With the above described arrangement it will be seen that in addition to providing a construction wherein the bearing serves as a part of the packing for the rotor I provide at the same time a construction wherein the bearing and packing are supported by and arranged in the same housing. This arrangement is of advantage in that it gives a compact construction and one which can be manufactured and installed at relatively low 7 cost.

In accordance with the provisions of the patent statutes I have described the principle of operation of my invention, together with the apparatus which I consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown and described is only illustrative and that the invention may be carried out by other means.

What I claim as new and desireto secure by Letters Patent of the United States, is:

1.' Sealing means fora centrifugal compressor or blower having a shaft and an impeller overhung on the end of the shaft with its suction side facing away from the shaft, comprising a bearing for the shaft, a casing for the impeller, a packing located between the shaft and said casin directly adacent to said bearing, walls de nil-1g a sealed chamber between the adjacent ends of the bearing and packing, a pipe for conveying lubricant from said sealed chamber, and means providing a liquid seal for saidpipe.

*2. Sealing means for a centrifugal compressor or blower provided with a casing having a suction inlet on one side, a housing connected to its other side, .a shaft, and an impeller overhung on the end of said shaft, comprising, a bearing in the housing for the shaft, a packing for the shaft, located directly adjacent to the end of said bearing and supported by said housing, walls defining a sealed chamber between the adjacent ends of the bearing and the packing, a pipe for conveying lubricant from said sealed chamber and means providing a liquid seal for .said pipe.

3. Sealing means for acentrifugal compressor or blower provided with a casing having a suction inlet on one side, a housing connected to its other side, a shaft, and an. impeller overhung on the end of the shaft, comprising, a bearing in the housing for the shaft, a packing for the shaft located adjacent to the end of said bearing, walls defining a sealed chamber between the adjacent ends of the bearing and the packing, a drain for said chamber and means forming a seal for said drain, said packing being so constructed and arranged that the pressure of the gas leaking from it is equal substantially to the pressure of the oil flowing from the bearing end.

In witness whereof, I have hereunto :set my hand this 12th day of November, 1928.

BRUNO HOFFMANN. 

